Maybe you have heard that you should harden off plants before transplanting them outside. What does harden off plants mean and how long does it take to harden off plants? ? What happens if you don’t harden off plants? Read on to find out!
You have been growing some seedlings (young plants) inside. Maybe you have told your friends about the seedlings, taken photos and named the baby plants. Whether you grew your seedlings from seed or purchased the seedlings from a garden store, you have watered them, given them light, and oohed and aahed over them. Likely, you have even talked to them (like I do). No matter what you have done, you are a proud parent of tiny plants that are only a few weeks old. After all your work, you’re eager to watch the plants grow outside and eventually produce food.
So, you know your young plants need to be transplanted outside, but how?
What Does Harden Off Plants Mean?
Those young plants (seedlings) have grown indoors where their light, temperature, water, and the air around them has been controlled — by you, by the nursery, or both. First, your seedlings need to get ready for the elements of the unpredictable, great outdoors. Your seedlings’ new, outdoor environment will have wind, rain, sunshine, and possibly even a light frost—all elements that don’t exist inside where you have been raising them.
Hardening off plants is simply the process of gradually helping plants adapt to a different environment (the sun, wind, rain, and temperatures of the outside world).
What Happens If You Don’t Harden Off Plants?
If you don’t harden off your seedlings, the plants might have stunted growth or even die. Nobody wants that, especially after all the work and time you have put into growing your plants indoors.
Now that you know what hardening off seedlings means, how long does it takes to harden off plants?
How Long Does It Take To Harden Off Plants?
For me, being patient can be one of the hardest parts of growing my own food.
Hardening off and transplanting is slow-going, but critical to keeping your baby plants healthy and helping them grow.
How long it takes to harden off your plants depends on the plants’ health, the weather, and how long you expose the plants to their new environment each day. Typically, the process of hardening off takes 7 to 14 days.
How Do You Harden Off Plants?
One to two weeks before you plan to transplant them outside, begin to harden off your seedlings.
Choose a spot outside to place the seedlings. Make sure that spot is in partial shade and away from pets and other animals.
Place the plants outside in their pots every day for 7 to 14 days. Each day, gradually increase the time the plants spend outside.
Here’s what this gradual exposure might be like for 7 days:
Day 1: After your last frost date, or when evening temperatures have consistently been above freezing, place the seedlings outside in the morning for 2 hours in your dedicated spot. This is the start of gradual exposure. Bring the seedlings back inside after the 2-hour period.
Day 2: Again, in the morning, place the seedlings outside at the same time in the morning and in your dedicated spot. This time, leave them outside for 4 hours. Bring the seedlings back inside after the 4-hour period.
Day 3: Place the seedlings outside in the morning in the same spot for 6 hours. Bring the seedlings back inside after 6 hours.
Day 4: Place the seedlings outside in the same spot for 8 hours. Again, bring the seedlings back inside at the end of the 8 hours. By now your seedlings are experiencing morning and afternoon conditions.
Day 5: Place the seedlings outside in the same spot for 10 hours. Again, bring the seedlings back inside at the end of the 10 hours.
Day 6: Early the next morning, place the seedlings outside in the same spot and leave for 12 hours. Your plants are almost ready for the new, outdoor home, so you can start preparing the outdoor soil. Add compost or any organic fertilizer, and anything else you know your plants need, to the garden.
Day 7: Transplant the seedlings into their permanent, outdoor home!
What Are Some Tips To Hardening Off Your Plants?
Start the hardening off process when you plan to be home so you can bring your plants indoors at your scheduled time. The example above hardened off the plants in the morning. If that doesn’t work for you, start hardening off your plants in the afternoon.
Make the process easy on your schedule. The number of hours mentioned above for each day is an approximate amount of time to leave your seedlings outdoors. You might have to slightly change the number of hours or time of day to suit your busy schedule or to work with the weather.
Overcast days are ideal for transplanting because direct sun can shock the plants. If it’s predicted to be a hot day, transplant the seedlings early in the morning so the seedlings aren’t immediately exposed to a hot, afternoon sun.
To give your seedlings a little extra love and nutrient boost during the week or two when they are hardening off, top up their pots with a small amount of compost or other organic fertilizer. I add vermicompost to mine.
Remember, the idea is to gradually increase the seedlings’ exposure to the outdoor temperatures, wind, sun, and rain. Patience, patience, patience.
Knowing what it means to harden off seedlings is important, and knowing how long it takes to harden off plants is key to your planning. You put care into giving your seedlings their best chance possible to thrive and produce food for you. Continue that care after they move outside to the garden. This blog post has some tips to help you keep your seedlings healthy as they move to their new home.
Now that you understand what hardening off plants means, and how long it can take to harden off plants, you can plan these extra few days into your planting schedule.
